Apparatus for making bag assembly

ABSTRACT

A welding apparatus includes first and second die members opposing one another. The first and second die members include opposing respective first and second perimeter-welding electrodes and opposing respective first and second tube-welding electrodes. The first perimeter-welding electrode and first tube-welding electrode define a first welding surface. The second perimeter-welding electrode and second tube-welding electrode define a second welding surface. A single source of high frequency energy is electrically connected to the perimeter-welding electrodes and to the tube-welding electrodes. Dielectric material is selectively disposed on the first welding surface such that the material is disposed on some but not all the first welding surface for reducing a strength of a high frequency electric field between the first and second perimeter-welding electrodes as compared to a strength of the high frequency electric field between at least a portion of the first and second tube-welding electrodes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. Ser. No.12/486,467, filed Jun. 17, 2009, the entire contents of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to an apparatus for forming abag assembly including a bag and a tube providing fluid communicationwith an interior of the bag.

BACKGROUND OF THE INVENTION

Welding by radiofrequency (RF) energy is an efficient and fast way tomanufacture certain products. For example, radiofrequency energy may beused to weld polymeric material, such as polyvinyl chloride (PVC), tomake flexible bags for retaining fluid. For example, a bag for receivingpressurized air is incorporated into a vascular compression device forpreventing pulmonary embolisms and deep vein thrombosis (DVT).

A bag of a typical vascular compression device includes a pair ofopposing polymeric sheets, such as PVC, welded around their perimetersand a polymeric tube port, such as PVC, welded between the sheets influid communication with the bag. An exemplary conventional process forforming the bag uses a die for welding the bags together and acylindrical mandrel for welding the polymeric sheets to the tube. Thecylindrical mandrel is inserted into the tube, and the mandrel, the tubeand the opposing sheets are compressed between the dies. Radiofrequencyenergy is supplied to the die to create a radiofrequency electric field.The electric field heats the polymeric sheets, thereby welding thesheets together form the perimeter of the bag.

After the bag is welded, the radiofrequency energy directed to the diesis stopped. Radiofrequency energy is then supplied to the mandrel sothat the radiofrequency electric field is directed outward in a radialdirection from the mandrel, through the tube and sheets. Theradiofrequency electric field heats the tube and the sheets, therebywelding the sheets to the tube and welding the tube in fluidcommunication with the bag.

The use of a cylindrical mandrel may be inefficient and time-consumingbecause of the difficulties in both inserting the mandrel into the tubeand removing the mandrel from the tube after the process.

In another exemplary process, the mandrel is replaced by a rigid,non-deformable tubular insert that is received in the tube. Like theabove process, radiofrequency energy is supplied to a die, for example,to create an electric field. However, in this process, the die includesportions that surround the tube and the tubular insert and direct theradiofrequency electric field into the tube and the sheets surroundingthe tube to weld them together.

Although this process purportedly welds both the bag and the tube to thebag at the same time and in one step, the use of a tubular insert,without more, is not sufficient to weld both the bag and the sheets tothe tube. Welding the sheets to the tube takes longer than welding thebag because the tube is typically thicker than the polymeric sheet. Ifthe process lasted long enough to adequately weld the sheets to thetube, then there is a risk that the die will cut or at least weaken thebag at the bag perimeter because of the amount of time the sheets wouldbe subjected to the electric field.

SUMMARY OF THE INVENTION

In one aspect a welding apparatus for use in one-step welding to form abag assembly comprising a bag and a tube in fluid communication with thebag generally comprises first and second die members opposing oneanother and defining a space therebetween for receiving opposing sheetsand a tube. The first and second die members include opposing respectivefirst and second perimeter-welding electrodes adapted to weld the sheetstogether to define a perimeter-weld of the bag and opposing respectivefirst and second tube-welding electrodes adapted to weld the sheets tothe tube to define a tube-weld so that the tube is in fluidcommunication with the bag. The first perimeter-welding electrode andfirst tube-welding electrode define a first welding surface. The secondperimeter-welding electrode and second tube-welding electrode define asecond welding surface opposing the first welding surface. A singlesource of high frequency energy is electrically connected to the firstand second perimeter-welding electrodes and to the first and secondtube-welding electrodes to produce a high frequency electric fieldbetween the perimeter-welding electrodes and the tube-weldingelectrodes. Dielectric material is selectively disposed on the firstwelding surface such that the material is disposed on some but not allthe first welding surface for reducing the strength of the highfrequency electric field between the first and second perimeter-weldingelectrodes as compared to a strength of the high frequency electricfield between at least a portion of the first and second tube-weldingelectrodes so that the sheets are welded to the tube and the sheets arewelded together in a single welding operation.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of one embodiment of a bag assembly;

FIG. 2 is section of the bladder assembly taken in the plane includingthe line 2-2 of FIG. 1;

FIG. 3 is an enlarged fragmentary section of the bladder assembly takenin the plane including the line 3-3 of FIG. 1;

FIG. 4 is a schematic elevation of one embodiment of a welding apparatusfor manufacturing the bladder assembly of FIG. 1;

FIG. 4A is an enlarged, fragmentary perspective of a lower die member ofthe welding apparatus;

FIG. 5 is a plan view of an upper die member of the welding apparatus;

FIG. 6 is a plan view of the lower die member of FIG. 4;

FIG. 7 is a perspective of the tube-welding portion of the upper diemember;

FIG. 8 is a front elevation of the tube-welding portions forming atube-weld of the bladder assembly, electrical flow of radiofrequencyenergy from a radiofrequency generator being shown schematically;

FIG. 9 is an enlarged, fragmentary section of the upper and lower diemembers with the upper die member in an initial configuration and abladder subassembly disposed between the upper and lower die members;

FIG. 9A is an enlarged section taken in the plane of lines 9A-9A of FIG.9;

FIG. 10 is an electrical schematic representing components of thetube-welding and perimeter-welding portions as electrical components;

FIG. 11 is similar to FIG. 9 with the upper die member being in aprimary welding configuration, in which a perimeter-weld and a tube-weldare being formed on the bladder assembly;

FIG. 12 is a view similar to FIG. 9 showing an embodiment wheredielectric material has been placed at alternative locations;

FIG. 13 is a schematic view of an alternative embodiment of a weldingapparatus having different upper and lower die members compared to theprevious embodiment;

FIG. 14 is a plan view of the lower die member of FIG. 13;

FIG. 14A is an enlarged section taken in the plane of lines 14A-14A ofFIG. 14;

FIG. 15 is a schematic elevation of a third embodiment of a weldingapparatus for manufacturing the bladder assembly of FIG. 1;

FIG. 16 is a plan view of the lower die member of FIG. 15;

FIG. 17 is an enlarged, fragmentary section of the upper and lower diemembers with the upper die member in an initial configuration and abladder subassembly disposed between the upper and lower die members ofthe second embodiment; and

FIG. 18 is similar to FIG. 17 with the upper die member being in aprimary welding configuration, in which a perimeter-weld and a tube-weldare being formed on the bladder assembly.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, and in particular to FIG. 1, a bagassembly is generally indicated at 10. The bag assembly is constructedfor use with a vascular compression device and is often referred to inthe art as a bladder assembly. The assembly includes a number of tubes12, each being in sealed fluid communication with an interior 14 (FIG.2) of a respective bladder 16 at a tube port generally indicated at 18(FIG. 3). Opposed sheets 20 are welded together along perimeter-welds 22to define the three bladders 16. It will be understood that the bladders16 in the bladder assembly 10 can be of any desired number, as can thenumber of tubes 12 in each bladder. The use of a bag assembly for otherthan a vascular compression device, including use to hold a liquid, iswithin the scope of the present invention.

Each tube port 18 includes a tubular insert 25 in the tube 12 for use inwelding the sheets 20 to the tube 12. The tubular insert 25 is explainedin more detail below. The tubes 12 are welded between the opposed sheets20 at tube-welds, generally indicated at 24, so that each of the tubesis sealed with the interior 14 of one of the bladders 16, and so thatfluid communication with the interior of the bladder occurs only throughthe tube port 18 (FIGS. 1 and 3). Each tube-weld 24 includes acircumferential-weld area 26 that extends around a circumference of thetube 12 and a pair of opposed lateral-weld areas 28 that extendlaterally from the circumferential-weld area at opposite lateral sidesof the tube. The lateral-weld areas 28 are contiguous with thecircumferential-weld area 26 and the perimeter weld 22 defining thebladder 16. At a later stage of production of the vascular compressiondevice, a connector (not shown) may be secured to ends of the tubes 12.The connector secures the tubes to an air compressor for introducingpressurized air into the bladders 16. As is known to those skilled inthe art, other layers of material may be applied onto the bladderassembly 10 to complete production of the vascular compression device.Moreover, the sheets 20 forming the bladders 16 may have any number oflayers of material. Moreover still, instead of securing full lengthtubes 12 to the sheets 20, short pieces of tubing (not shown) may besecured to the sheets, and at a later stage of production, full lengthtubes may be secured to the short pieces. Other arrangements are withinthe scope of the invention.

Referring to FIGS. 4-11, an exemplary embodiment of a welding apparatusfor making the bladder assembly 10 is generally indicated at 30. Theapparatus 30 includes a die 32 comprising an upper (broadly, first) diemember, generally indicated at 34, and an opposing lower (broadly,second) die member, generally indicated at 36. A press device 38 of thewelding apparatus 30 presses the opposed sheets 20 and the tube 12disposed between the sheets between the die members 34, 36. Aradiofrequency (RF) generator 40 (broadly, a source of radiofrequencycurrent) electrically connected to the die 32 creates a radiofrequencyfield between the die members 34, 36 that heats the sheets 20 and thetube 12 to weld the sheets into a bladder 16 and to weld the sheets tothe tube. Prior to being welded together, the sheets 20 and tube 12 maybe referred to as a “bladder assembly” and, more broadly, as a “bagassembly.” Other components may be included in the subassembly and somecomponents may be already connected together within the scope of thepresent invention. The bladder subassembly is generally indicated at 42in FIG. 9. The welding apparatus 30 also includes a microcontroller 44for integrating control of the press device 38 and the source ofradiofrequency generator 40.

As shown best in FIGS. 4A-6, each die member 34, 36 comprises aperimeter-welding portion, generally indicated at 46A and 46B,respectively, for welding the sheets 20 together to define the perimeterof the bladder 16 and a tube-welding portion, generally indicated at 48Aand 48B, for welding the sheets around the tube 12. Because each diemember 34, 36 includes one perimeter-welding portion 46A, 46B and onetube-welding portion 48A, 48B and because the bladder assembly 10 hasmore than one bladder 16 (i.e., three bladders), more than one operationmust be performed to make the separate bladders of the bladder assembly.For example, there may be three separate welding apparatuses along aconveyor for welding the three separate bladders 16. It is understoodthat the welding apparatus 30 may be configured to weld any number ofbladders of a single bladder assembly during the same operation. Forexample, the welding apparatus 30 may include more than one die forforming more than one bladder of the bladder assembly simultaneously.Alternatively, the welding apparatus may include a single die that hasmultiple (e.g., three) perimeter-welding portions 46A, 46B and multiple(e.g., three) tube-welding portions 48A, 48B. For clarity and forpurposes of this discussion, the illustrated welding apparatus 30 hasonly one pair of perimeter-welding portions 46A, 46B and one pair oftube-welding portions 48A, 48B for forming one bladder 16 of the bladderassembly 10 per operation.

Referring to FIGS. 4 and 5, the perimeter-welding portion 46A of theupper die member 34 includes an upper (broadly, first) perimeter-weldingblock 50 and an upper (broadly, first) perimeter-welding electrode 52protruding down from the upper block. The radiofrequency generator 40 iselectrically connected to the electrode 52 via the upperperimeter-welding block 50. The electrode 52 is elongate and has a shapeor outline corresponding generally to the shape of the perimeter of thebladder 16, except that the electrode is not continuous. That is, theelectrode 52 has spaced apart ends. The perimeter-welding portion 46B ofthe lower die member 36 includes a lower (broadly, second)perimeter-welding block 54 and a lower (broadly, second)perimeter-welding electrode 56 protruding upward from the lower block(FIGS. 4, 4A and 6). The lower perimeter-welding block 54 iselectrically grounded. The shape of the electrode 56 is a minor image ofthe upper perimeter-welding electrode 52, and both electrodes areillustrated as ribbon electrodes. The electrodes 52, 56 may be of otherconstructions. For example, either the upper or the lowerperimeter-welding electrode 52, 56, respectively, may comprise a nestfor receiving the other electrode, or either the upper or the lowerperimeter-welding electrode may be a planar surface. Otherconfigurations are within the scope of this invention. Theperimeter-welding blocks 50, 54 and electrodes 52, 56 may be formed fromany electrically conductive material. For example, the electrodes 52, 56may be constructed of brass or copper or aluminum or stainless steel ormagnesium and/or may be copper-plated or brass-plated.

Referring to FIGS. 7-9, each of the tube-welding portions 48A, 48B ofthe upper and lower die members 34, 36, respectively, includes atube-welding block 58A, 58B, respectively, and a tube-welding electrode,generally indicated at 60A, 60B, respectively, on the tube-weldingblock. The tube-welding blocks 58A, 58B are secured to respectiveperimeter-welding blocks 50, 54 so that tube-welding electrodes 60A, 60Bare disposed between opposite ends of the respective perimeter-weldingelectrodes 52, 56. The tube-welding blocks 58A, 58B are secured in fixedposition to respective perimeter-welding blocks 50, 54 by suitablemeans. The tube-welding blocks 58A, 58B and electrodes 60A, 60B areelectrically connected to the respective perimeter-welding blocks 50, 54and electrodes 52, 56, so that the upper tube-welding block 58A iselectrically connected to the radiofrequency generator 40 and the lowertube-welding block 58B is electrically grounded. It will be appreciatedthat the electrical connection can be reversed within the scope of thepresent invention.

Alternatively, the tube-welding blocks 58A, 58B and electrodes 60A, 60Bmay be movable in recesses in respective perimeter-welding blocks 50,54, as described in Applicants' co-pending application Ser. No.11/613,694, Publication No. US 2008/0149609, entitled Apparatus andMethod for Making Bag Assembly, incorporated herein by reference.

Referring to FIGS. 7 and 8, each tube-welding electrode 60A, 60Bincludes a concave, arcuate surface 64A, 64B, respectively, andopposite, planar lateral surfaces 66A, 66B, respectively. The concave,arcuate surfaces 60A, 60B are sized and shaped to substantiallycompletely surround the axial portion of the tube 12 to be welded in thebladder assembly 10 when the bladder subassembly 42 is pressed betweenthe die members 34, 36. The radiofrequency (RF) electric field appliedbetween these concave surfaces 64A, 64B forms the circumferential-weldarea 26 of the tube-weld 24 (see FIG. 3). The concave, arcuate surfaces64A, 64B generally have depths and widths slightly greater than theradius of the tube 12 to accommodate the thicknesses of the sheets 20overlying and underlying the tube. Likewise, the radiofrequency fieldapplied between the lateral surfaces 66A, 66B of the electrodes 60A, 60Bforms the lateral-weld areas 28 of the tube-weld 24. The tube-weldingblocks 58A, 58B and electrodes 60A, 60B may have other shapes and may beformed from any electrically conductive material. For example, theelectrodes 60A, 60B may be constructed of brass or copper or aluminum orstainless steel or magnesium and/or may be copper-plated orbrass-plated.

In general, the perimeter-welding electrodes 52, 56 and the tube-weldingelectrodes 60A, 60B are configured so that the strength of theelectrical field between the perimeter-welding electrodes is less thanthe strength of the electrical field between the tube-weldingelectrodes, at least in the area(s) between the tube-welding electrodeswhere the components to be welded (tube 12 and sheets 20) have acombined thickness greater than the combined thickness of the componentsto be welded (sheets 20 only) between the perimeter-welding electrodes.By varying the strength of the electric field between theperimeter-welding electrodes 52, 56 relative to the strength of electricfield between the tube-welding electrodes 60A, 60B, the perimeter-weld22 and tube-weld 24 can be completed substantially simultaneously in asingle welding operation and using a single source of high frequencyenergy (e.g., RF generator 40). As used in this context, “substantiallysimultaneously” means that the perimeter and tube-welds 22, 24 areformed during the same (coincident) or overlapping time periods. Asdescribed below, the relative strengths of the electric field betweenthe perimeter-welding electrodes 52, 56 and the tube-welding electrodes60A, 60B can be controlled by using dielectric material between theelectrodes.

Referring to FIG. 8, dielectric material 68 (e.g., nylon, Delrin,phenolic resins such as Bakelite, or any other resin-based dielectricmaterial) is connected to the planar lateral surfaces 66A, 66B of theupper and lower tube-welding electrodes 60A, 60B but not to the arcuate,concave surfaces 64A, 64B of the electrodes. The dielectric material 68contacts the sheets 20 in the lateral-weld areas and has a selectedthickness and a selected dielectric constant so that the lateral-weldareas 28 and the circumferential-weld area 26 are formed atsubstantially the same rate. (Determination of the proper thickness anddielectric constant of the dielectric material 68 to ensure properwelding is generally referred to as “tuning.”) In this regard, thedielectric material 68 on the lateral surfaces 66A, 66B of theelectrodes decreases the strength of the electric field in thelateral-weld areas 28 so as to slow heating to a rate that issubstantially similar to the heating rate of the tube 12 and theportions of the sheets 20 surrounding the tube. As is known in the art,the circumferential-weld area 26 of the tube-weld 24 is heated at aslower rate than the lateral-weld areas 28 due to the thickness of thetube 12. Thus, without the dielectric material 68, one of two situationsmay arise. If the tube-welding portion 48A of the upper die member 34 isnot removed from the sheets 20 until after the circumferential-weld area26 is complete, there is a risk that the lateral-weld areas 28 will burnor will thin out and weaken. On the other hand, if the tube-weldingportion 48A is removed from the sheets 20 immediately after thelateral-weld areas 28 are complete, there is a risk that thecircumferential-weld area 26 will not be fully forded. The use ofdielectric material 68, however, varies the strength of the electricfield over the tube-weld 26 (i.e., a greater strength in thecircumferential-weld area 26 compared to the lateral-weld areas 28) andallows for the different areas of the tube-weld to be completed atsubstantially the same time, thus avoiding the problems of weakening theweld or making an incomplete weld.

Referring to FIG. 9, dielectric material 72 (e.g., nylon, Delrin,phenolic resins such as Bakelite, or any other resin-based dielectricmaterial) is also provided between the upper and lower perimeter-weldingelectrodes 52, 56 of the upper and lower die members 34, 36. Thedielectric material 72 is “tuned” to have a selected thickness and aselected dielectric constant such that when RF energy is supplied to thedie from the RF source 40, the strength of the electrical field betweenthe perimeter-welding electrodes 52, 56 is less than the strength of theelectrical field between the tube-welding electrodes 60A, 60B, at leastin the circumferential-weld area 26. This variation in strengthcompensates for the fact that the combined thickness of the sheets 20 inthe perimeter-weld area 22 is less than the combined thickness of thesheets 20 and tube 12 in at least the circumferential-weld area 26 ofthe tube-weld 24. The dielectric material 72 between theperimeter-welding electrodes 52, 56 decreases the amount ofradiofrequency (RF) energy being supplied to the sheets 20 in theperimeter-weld area 22 so as to slow heating to a rate that issubstantially similar to the heating rate of the tube 12 and theportions of the sheets 20 surrounding the tube in thecircumferential-weld area 26 of the tube-weld 24. Without the dielectricmaterial between the perimeter-welding electrodes 52, 56, one of twosituations may arise. If the tube-welding portions 48A, 48B andperimeter-welding portions 46A, 46B of the die members 34, 36 are notremoved from the sheets until after the tube-weld 24 is complete, thereis a risk that the perimeter-welding electrodes 52, 56 will burn or thinout and weaken the perimeter-weld 22. On the other hand, if thetube-welding and perimeter-welding portions are removed from the sheetsimmediately after the perimeter-weld 22 is complete, there is a risk thetube-weld 24 will not be fully formed. The dielectric material 72 on oneor both of the perimeter-welding portions 46A, 46B allows both thetube-weld 24 and the perimeter-weld 22 to be completely formedsubstantially simultaneously in one welding operation.

The dielectric material 68, 72 between the planar lateral surfaces 66A,66B of the upper and lower tube-welding electrodes 60A, 60B and betweenthe upper and lower perimeter-welding electrodes 52, 56 may be securedonly to the upper electrodes 60A, 52, or only to the lower electrodes60B, 56, or to both of the upper and lower electrodes 60A, 60B, 52, 56,or to any combination of upper and lower electrodes. In the illustratedexample, the dielectric material or elements 68, 72 are suitably securedto both the upper and lower tube-welding electrodes 60A, 60B and to theupper and lower perimeter-welding electrodes 52, 56. In any case, thedielectric elements 68, 72 have selected thicknesses and selecteddielectric constants so that the perimeter-weld 22 and tube-weld 24 areformed substantially simultaneously and completely in one weldingoperation. In this regard, the thickness and/or dielectric constant ofthe dielectric material 68 on the lateral surfaces 66A, 66B of thetube-welding electrodes 60A, 60B may be different from the thicknessand/or dielectric constant of the dielectric material 72 on theperimeter-welding electrodes 52, 56. Further, the thickness and/ordielectric constant of the dielectric material 68, 72 on portions of theupper electrodes (e.g., the lateral surfaces 66A of the tube-weldingelectrode 60A or the perimeter-welding electrode 52) may be differentfrom the thickness and/or dielectric constant of the dielectric material68, 72 on corresponding portions of the lower electrodes 60B, 56. Bythus tuning the dielectric material 68, 72, the relative strengths ofthe electric field between the various portions of the upper electrodes52, 60A and lower electrodes 56, 60B can be controlled to achievesimultaneous formation of the perimeter-weld 22 and the tube-weld 24 sothat the entire process can be completed in one welding operation.

FIG. 9A illustrates one method of securing a dielectric element to a diecomponent such as a tube-welding electrode 60A, 60B or a perimeterwelding electrode 52, 56. In FIG. 9A, the dielectric element 72 isformed as a cap which has releasable dovetail connection with theelectrode 56 for easy replacement of the element in the event of damageor wear. Other types of releasable mechanical connections between theelement 72 and the electrode 56 can be used. Alternatively, theconnection can be achieved by a suitable molecular bond adhesive, epoxy,or high-temperature glues compatible with the dielectric material.

Referring to FIGS. 9-11, during operation the radiofrequency generator40 delivers radiofrequency (RF) energy to the upper tube welding portion48A and upper perimeter welding portion 46A. The radiofrequency energyflows from the upper tube-welding portion 48A through the opposingsheets 20 and the tube 12 to the lower tube-welding portion 48B.Similarly, the radiofrequency energy flows from the upperperimeter-welding portion 46A through the opposing sheets 20 to thelower perimeter-welding portion 46B. This flow of radiofrequency energycan be modeled by an electrical circuit, generally designated byreference numeral 69 in FIG. 10. Opposite lateral surfaces 66A, 66B anddielectric material 68 of the upper and lower tube-welding electrodes60A, 60B can be modeled by capacitors C1 and C2. The arcuate surface 64Aof the upper tube-welding electrode 60A and an upper portion of thetubular insert 25 can be modeled by a capacitor C3. The arcuate surface64B of the lower tube-welding electrode 60B and a lower portion of thetubular insert 25 can be modeled by a capacitor C4. The upper and lowerperimeter-welding electrodes 52, 56 and dielectric material 72 can bemodeled by capacitor C5. In the electrical circuit 69, the capacitorsC1, C2 and C5 are connected in parallel to each other and to thecapacitors C3 and C4, which are connected in series. Generally, thefollowing relationship for capacitance of the capacitors C1-C5 should beachieved for uniform welding of the perimeter weld 22 and tube-weld 24:(1/C3)+(1/C4)=(1/C1)=(1/C2)=(1/C5). In other words, the dielectricmaterial 68 between the lateral surfaces 66A, 66B of the tube-weldingelectrodes 60A, 60B must be adjusted to allow relatively moreradiofrequency energy to be directed to the capacitors C3 and C4 (i.e.,to the circumferential weld 26). The thickness and dielectric constantof the dielectric material 68 is such that the circumferential-weld area26 is formed at substantially the same rate as the lateral weld areas 28of the tube-weld 24. Similarly, the thickness and dielectric constant ofthe dielectric material 72 is such that the perimeter-weld 22 is formedat substantially the same rate as the tube-weld 24. Desirably, all RFdie components receive the same amount of RF energy required to completetheir respective welds within the same welding time allotment.

An exemplary process of forming the bag assembly 10 is now disclosed.The tubular insert 25 is inserted in the polymeric tube 12. The tubularinsert 25 may be formed from a non-ferrous metal, such as brass orcopper or aluminum or stainless steel or other material. Alternatively,the insert 25 may be formed from a material that is resilientlydeformable in a radial direction and has either a higher meltingtemperature than the polymeric tube or is substantially insusceptible ofbeing heated by radiofrequency energy. The insert 25 is sized and shapedto fit snugly within the axial portion of the tube 12 that is to bewelded to sheets 20. Thus, the insert 25 may have a length that issubstantially the same as the length of the arcuate tube-weldingsurfaces 64A, 64B of the tube-welding portions 48A, 48B of the diemembers 34, 36. It is understood that the insert 25 may have othersizes, for example, it may extend the full length of the tube. Moreover,it is understood that in lieu of the resiliently flexible insert 25, theinner surface of the tube 12 may be coated with a material that haseither a higher melting temperature than the polymeric tube or isincapable of being heated by radiofrequency energy. Applicants'co-pending application Ser. No. 11/613,694, Publication No. US2008/0149609, entitled Apparatus and Method for Making Bag Assembly,describes the resiliently deformable tubular insert 25 in detail, and isincorporated herein by reference in its entirety.

The tube 12 with the tubular insert 25 is placed between the polymericsheets 20 to form the bag (e.g., bladder) subassembly 42. Using thepress device 38, the upper die member 34 is positioned in an initialposition in which the upper die member is disposed above the lower diemember 36 a distance D1 (FIG. 9). The distance D1 should be such thatthe bag subassembly 42 can be placed between the die members 34, 36. Thebag subassembly is then placed on the lower die member. It is understoodthat the bag subassembly may be preassembled and then placed between thedie members, as described above, or may be assembled between the diemembers.

After the bag subassembly 42 is placed between the die members 34, 36,the press device 38 is activated to lower the upper die member 34 to awelding position in which both the tube-welding portions 48A, 48B andthe perimeter-welding portions 46A, 46B of the die members 34, 36compress the bag subassembly (FIG. 11). RF current from the generator 40is supplied to the perimeter-welding portion 46A and the tube-weldingportion 48A of the upper die member 34. The current creates an electricfield modulated in the radiofrequency range (broadly, radiofrequencyenergy) between the tube-welding portions 48A, 48B of the upper andlower die members 34, 36 and between the perimeter-welding portions 46A,46B of the die members. Due to the tuning of the dielectric material 68,72 on the upper and lower electrodes, the strength of the electricalfield generated between the electrodes varies as needed to effectsimultaneous formation of the perimeter-weld 22 and the tube-weld 24.Specifically, the tube 12 and corresponding portions of the sheets 20surrounding the tube in the area of the tube-weld 24 having a relativelygreater thickness are subjected to a relatively stronger electric field,and the sheets 20 between the perimeter-welding electrodes 52, 56 havinga relatively smaller thickness, are simultaneously subjected to arelatively weaker electric field. As a result, the tube-weld 24 and theperimeter-weld 22 of the bag assembly are properly (fully andcompletely) formed substantially simultaneously in one weldingoperation.

After the tube-weld 24 and perimeter-weld 22 are complete, the pressdevice 38 lifts the upper die member 34 back to its initialconfiguration so that the upper tube-welding electrode 60A and the upperperimeter-welding electrode 52 are not in contact with the formed bagassembly 10. At this point, the assemblage of the bag assembly issubstantially complete, i.e. the bladder 16 is formed and the tube port18 is welded in fluid communication with the bladder.

As described above, the dielectric material 72 reduces the strength ofthe electrical field between the perimeter-welding electrodes 52, 56 sothat the perimeter weld and tube-weld 24 are completed substantially atthe same time. In the embodiment of FIGS. 1-11, the dielectric materialis illustrated as being secured to the outer edges of theperimeter-welding electrodes. However, the dielectric material can bepositioned at other locations for reducing the strength of theelectrical field between the perimeter-welding electrodes. For example,as shown in FIG. 12, a sheet 72′ of dielectric material may be placedbetween the base of the perimeter-welding electrode 52′ and theperimeter-welding block 50′ of the first die member 34′. A similar sheet72′ may be placed between the base of the perimeter-welding electrode56′ and the perimeter-welding block 54′ of the second die member 36′.Other arrangements are possible.

The opposing die members 34, 36 can have configurations other than asdescribed in the previous embodiments. For example, FIGS. 13, 14 and 14Ashow an embodiment in which the two die members 34′ and 36′ are notmirror images of one another. In this embodiment, the first (upper) diemember 34′ is substantially identical to the first die member 34 of thefirst embodiment, and corresponding parts are designated bycorresponding reference numbers plus a prime (′) designation. On theother hand, the second (lower) die member, designated 36′, has asubstantially flat, continuous, planar surface 150 that opposes thefirst die member 34′. The surface 150 has no projecting members.Instead, the surface 150 is recessed to have a relatively small concave,arcuate surface 64B′ and two co-planar flat lateral surfaces 66B′ onopposite sides of the concave surface 64B′. The concave surface 64B′ iscomplementary to the concave, arcuate surface 64A′ of the tube-weldingelectrode 58A′ on the opposing die member 34′. The two surfaces 64A′,64B′ define the circumferential-weld area of the tube-weld 24.Dielectric elements 68′ are secured (e.g., by adhesive) to the recessedlateral surfaces 66B′ of the second die 36′ at opposite sides of thearcuate surface 64B′. The upper surfaces of these elements 68′ aregenerally co-planar with the surface 150 and are located generallyopposite the dielectric elements 68′ on the tube-welding electrode 60A′of the opposing die member 34′ to define the lateral-weld areas of thetube-weld. Unlike the first die member 34′, the second die member 36′has no perimeter-welding electrode projecting from surface 150. Instead,the perimeter-welding electrode of the second die member is defined byan area 160 (or areas) of the surface 150 generally opposing the firstperimeter-welding electrode 52′ (see FIG. 14).

Referring now to FIGS. 15-18, another embodiment of a welding apparatusfor manufacturing the bag assembly is generally indicated at 200. Thisembodiment is substantially similar to the embodiment of FIGS. 1-11, andcorresponding parts are indicated by corresponding reference numerals.However, the welding apparatus 200 of this embodiment includes a stopdevice, generally designated 206, for limiting movement of the opposingperimeter-welding portions 46A, 46B of the two die members 34, 36 towardeach other to prevent excessive displacement of sheet material in theperimeter-weld 22 by engagement with the perimeter-welding portions. Bylimiting penetration of the die members into the heated sheet materialduring the welding process, the perimeter-welding portions 46A, 46B canbe held in position for a longer length of time without damage (e.g.,overheating, thinning) to the perimeter-weld 22, thus allowing thetube-weld 24 a longer time in which to fully form. As a result, both theperimeter-weld 22 and the tube-weld 24 can be completed in a singlewelding operation. In embodiments where each die member 34, 36 isconstructed so that the tube-welding portion 48A, 48B of the die memberis fixed and immovable relative to the perimeter-welding portion 46A,46B of the die member, the stop device 206 will also limit movement ofthe opposing tube-welding portions of the two die members toward eachother to prevent excessive displacement of sheet material in thetube-weld 24 by engagement with the tube-welding portions. However, inembodiments where the tube-welding portion 48A, 48B of a die member 34,36 is movable relative to the perimeter-welding portion 52, 56 of thedie member, as is described in Applicants' aforementioned co-pendingapplication Ser. No. 11/613,694, Publication No. US 2008/0149609, thestop device 206 may or may not limit the opposing tube-welding portions206 of the two die members toward each other. In general, however, thespacing between all welding surfaces must be controlled to achieveproper one-step welding.

Desirably, the stop device 206 comprises at least one stand-off in theform of one or more columns 210 (broadly, a stop structure) disposedbetween the opposing die members 34, 36 for limiting movement of atleast the opposing perimeter-welding portions 46A, 46B toward eachother. As illustrated in FIG. 16, the columns are generally cylindricaland positioned along a perimeter of the perimeter-welding portion 46B ofthe lower die member 36. It is understood that the column(s) 210 mayhave other shapes. Further, a single, continuous stop structure may beused. In any case, the stop device 206 may comprise structure on thelower die member 36 (as shown) or on the upper die member 34 or on bothdie members.

Referring to FIGS. 17 and 18, the stop device 206 extends up from thelower die member 36 a distance D2. In general, the magnitude of thisdistance D2 is such that when the stop device contacts theperimeter-welding block 50 of the upper die member 34, the space or gap212 between the perimeter-welding portions 46A, 46B of the upper andlower die members 34, 36 is desirably approximately equal to, and notsubstantially less than, the desired thickness of the finalperimeter-weld 22 in the bag assembly 10. As a result, the stop device206 limits penetration of the perimeter-weld portions 46A, 46B into theheated sheet material during the welding process, thereby avoidingexcessive displacement of sheet material and undesirable burning and/orthinning of the perimeter-weld 22. (The excessive displacement would becaused by the pressure contact of the perimeter-welding electrodes 52,56 or any dielectric material 72 thereon with the heated sheetmaterial.) By way of example, as illustrated in FIG. 18, the stop device206 may set the minimum gap 212 between the perimeter-welding portions46A, 46B to a distance that corresponds to the desired final thicknessof the perimeter-weld, which may vary according to each material typeand/or material thickness. In any event, the stop device 206 should notadversely affect the operation of the tube-welding portions 48A, 48B ofthe die members 34, 36.

The stop device 206 can be configured to increase or decrease theminimum space or gap 212 between the perimeter-welding portions 46A, 46Bof the upper and lower die members 34, 36. By way of example, if thestop device 206 comprises one or more columns 210 (as illustrated), thelengths of the columns can be varied to provide the desired gap 212. Inthis way, excessive penetration of the weld areas by the dielectricmaterial on the electrodes, or by the electrodes if there is nodielectric material on them, is avoided.

Other ways of limiting the movement of at least the perimeter-weldingportions 46A, 46B of the upper and lower die members 34, 36 toward oneanother are within the scope of this invention.

It is understood that the stop device 206 can be used in embodimentswhere one or more of the electrodes 52, 56, 60A, 60B include dielectricmaterial 68, 68′, 72, 72′ (as described above) and in embodiments whereone or more of the electrodes 52, 56, 60A, 60B do not include dielectricmaterial. Further, the teachings above regarding the use of a stopdevice and dielectric material on the perimeter-welding electrodes 52,56 can be applied to the welding apparatus disclosed in Applicants'aforementioned co-pending application Ser. No. 11/613,694, PublicationNo. US 2008/0149609 entitled Apparatus and Method for Making BagAssembly. Also, the stop device 206 can be used in embodiments where theopposing die members are not mirror images of one another. For example,as discussed above in regard to the embodiment of FIGS. 13 and 14, oneof the die members, like the die member 34′, may have a flat,continuous, planar surface without projecting electrodes.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the terms “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions, products,and methods without departing from the scope of the invention, it isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

1. Welding apparatus for use in one-step welding to form a bag assemblycomprising a bag and a tube in fluid communication with the bag, thewelding apparatus comprising: first and second die members opposing oneanother and defining a space therebetween for receiving opposing sheetsand a tube, the first and second die members including opposingrespective first and second perimeter-welding electrodes adapted to weldthe sheets together to define a perimeter-weld of the bag and opposingrespective first and second tube-welding electrodes adapted to weld thesheets to the tube to define a tube-weld so that the tube is in fluidcommunication with the bag, the first perimeter-welding electrode andfirst tube-welding electrode defining a first welding surface, and thesecond perimeter-welding electrode and second tube-welding electrodedefining a second welding surface opposing the first welding surface; asingle source of high frequency energy electrically connected to thefirst and second perimeter-welding electrodes and to the first andsecond tube-welding electrodes to produce a high frequency electricfield between the perimeter-welding electrodes and the tube-weldingelectrodes; and dielectric material selectively disposed on the firstwelding surface such that the material is disposed on some but not allthe first welding surface for reducing the strength of the highfrequency electric field between the first and second perimeter-weldingelectrodes as compared to a strength of the high frequency electricfield between at least a portion of the first and second tube-weldingelectrodes so that the sheets are welded to the tube and the sheets arewelded together in a single welding operation.
 2. Welding apparatus asset forth in claim 1 wherein the dielectric material is disposed on anentirety of the first perimeter-welding electrode and only a portion ofthe first tube-welding electrode.
 3. Welding apparatus as set forth inclaim 2 further comprising a second dielectric material selectivelydisposed on the second welding surface such that the second dielectricmaterial is disposed on some but not all of the second welding surface,the second dielectric material opposing the dielectric material disposedon the first welding surface.
 4. Welding apparatus as set forth in claim3 wherein the second dielectric material is disposed on an entirety ofthe second perimeter-welding electrode and only a portion of the secondtube-welding electrode.
 5. Welding apparatus as set forth in claim 4wherein the second dielectric material on the second tube-weldingelectrode opposes the dielectric material on the first tube-weldingelectrode.
 6. Welding apparatus as set forth in claim 1 furthercomprising a stop device for limiting penetration of the firsttube-welding electrode and first perimeter-welding electrode into thesheets.